Authorities released a photo on Friday of the pair, a man and a woman, and the graffiti they allegedly left on rocks near the Yavapai Geology Museum. The words “Evans 16” were written in black spray paint on a rock feature, according to the National Parks Service's Investigative Services Branch.

The photos were snapped by another visitor on May 22 in the South Rim of the park. The visitor told investigators he or she saw the couple as they were spray painting the graffiti, according to NPS.

The pair left the park before park rangers could speak with them.

Anyone with information on the identities of the suspects can call NPS' Investigative Services Tip Line at 888-653-0009 or send authorities an online tip, an email or a Facebook message.